ovl: split super.c

fs/overlayfs/super.c is the biggest of the overlayfs source files and it
contains various utility functions as well as the rather complicated lookup
code.  Split these parts out to separate files.

Before:

 1446 fs/overlayfs/super.c

After:

  919 fs/overlayfs/super.c
  267 fs/overlayfs/namei.c
  235 fs/overlayfs/util.c
   51 fs/overlayfs/ovl_entry.h

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

6 files changed, 572 insertions, 546 deletions

diff --git a/fs/overlayfs/Makefile b/fs/overlayfs/Makefile
index 900daed3e91d..99373bbc1478 100644
--- a/fs/overlayfs/Makefile
+++ b/fs/overlayfs/Makefile
@@ -4,4 +4,4 @@
 
 obj-$(CONFIG_OVERLAY_FS) += overlay.o
 
-overlay-objs := super.o inode.o dir.o readdir.o copy_up.o
+overlay-objs := super.o namei.o util.o inode.o dir.o readdir.o copy_up.o
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
new file mode 100644
index 000000000000..f4057fcb0246
--- /dev/null
+++ b/fs/overlayfs/namei.c
@@ -0,0 +1,267 @@
+/*
+ * Copyright (C) 2011 Novell Inc.
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include "overlayfs.h"
+#include "ovl_entry.h"
+
+static struct dentry *ovl_lookup_real(struct dentry *dir,
+				      const struct qstr *name)
+{
+	struct dentry *dentry;
+
+	dentry = lookup_one_len_unlocked(name->name, dir, name->len);
+	if (IS_ERR(dentry)) {
+		if (PTR_ERR(dentry) == -ENOENT)
+			dentry = NULL;
+	} else if (!dentry->d_inode) {
+		dput(dentry);
+		dentry = NULL;
+	} else if (ovl_dentry_weird(dentry)) {
+		dput(dentry);
+		/* Don't support traversing automounts and other weirdness */
+		dentry = ERR_PTR(-EREMOTE);
+	}
+	return dentry;
+}
+
+static bool ovl_is_opaquedir(struct dentry *dentry)
+{
+	int res;
+	char val;
+
+	if (!d_is_dir(dentry))
+		return false;
+
+	res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
+	if (res == 1 && val == 'y')
+		return true;
+
+	return false;
+}
+
+/*
+ * Returns next layer in stack starting from top.
+ * Returns -1 if this is the last layer.
+ */
+int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	BUG_ON(idx < 0);
+	if (idx == 0) {
+		ovl_path_upper(dentry, path);
+		if (path->dentry)
+			return oe->numlower ? 1 : -1;
+		idx++;
+	}
+	BUG_ON(idx > oe->numlower);
+	*path = oe->lowerstack[idx - 1];
+
+	return (idx < oe->numlower) ? idx + 1 : -1;
+}
+
+struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
+			  unsigned int flags)
+{
+	struct ovl_entry *oe;
+	const struct cred *old_cred;
+	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+	struct path *stack = NULL;
+	struct dentry *upperdir, *upperdentry = NULL;
+	unsigned int ctr = 0;
+	struct inode *inode = NULL;
+	bool upperopaque = false;
+	bool stop = false;
+	bool isdir = false;
+	struct dentry *this;
+	unsigned int i;
+	int err;
+
+	old_cred = ovl_override_creds(dentry->d_sb);
+	upperdir = ovl_upperdentry_dereference(poe);
+	if (upperdir) {
+		this = ovl_lookup_real(upperdir, &dentry->d_name);
+		err = PTR_ERR(this);
+		if (IS_ERR(this))
+			goto out;
+
+		if (this) {
+			if (unlikely(ovl_dentry_remote(this))) {
+				dput(this);
+				err = -EREMOTE;
+				goto out;
+			}
+			if (ovl_is_whiteout(this)) {
+				dput(this);
+				this = NULL;
+				stop = upperopaque = true;
+			} else if (!d_is_dir(this)) {
+				stop = true;
+			} else {
+				isdir = true;
+				if (poe->numlower && ovl_is_opaquedir(this))
+					stop = upperopaque = true;
+			}
+		}
+		upperdentry = this;
+	}
+
+	if (!stop && poe->numlower) {
+		err = -ENOMEM;
+		stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
+		if (!stack)
+			goto out_put_upper;
+	}
+
+	for (i = 0; !stop && i < poe->numlower; i++) {
+		struct path lowerpath = poe->lowerstack[i];
+
+		this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
+		err = PTR_ERR(this);
+		if (IS_ERR(this)) {
+			/*
+			 * If it's positive, then treat ENAMETOOLONG as ENOENT.
+			 */
+			if (err == -ENAMETOOLONG && (upperdentry || ctr))
+				continue;
+			goto out_put;
+		}
+		if (!this)
+			continue;
+		if (ovl_is_whiteout(this)) {
+			dput(this);
+			break;
+		}
+		/*
+		 * If this is a non-directory then stop here.
+		 */
+		if (!d_is_dir(this)) {
+			if (isdir) {
+				dput(this);
+				break;
+			}
+			stop = true;
+		} else {
+			/*
+			 * Only makes sense to check opaque dir if this is not
+			 * the lowermost layer.
+			 */
+			if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
+				stop = true;
+		}
+
+		stack[ctr].dentry = this;
+		stack[ctr].mnt = lowerpath.mnt;
+		ctr++;
+	}
+
+	oe = ovl_alloc_entry(ctr);
+	err = -ENOMEM;
+	if (!oe)
+		goto out_put;
+
+	if (upperdentry || ctr) {
+		struct dentry *realdentry;
+		struct inode *realinode;
+
+		realdentry = upperdentry ? upperdentry : stack[0].dentry;
+		realinode = d_inode(realdentry);
+
+		err = -ENOMEM;
+		if (upperdentry && !d_is_dir(upperdentry)) {
+			inode = ovl_get_inode(dentry->d_sb, realinode);
+		} else {
+			inode = ovl_new_inode(dentry->d_sb, realinode->i_mode,
+					      realinode->i_rdev);
+			if (inode)
+				ovl_inode_init(inode, realinode, !!upperdentry);
+		}
+		if (!inode)
+			goto out_free_oe;
+		ovl_copyattr(realdentry->d_inode, inode);
+	}
+
+	revert_creds(old_cred);
+	oe->opaque = upperopaque;
+	oe->__upperdentry = upperdentry;
+	memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
+	kfree(stack);
+	dentry->d_fsdata = oe;
+	d_add(dentry, inode);
+
+	return NULL;
+
+out_free_oe:
+	kfree(oe);
+out_put:
+	for (i = 0; i < ctr; i++)
+		dput(stack[i].dentry);
+	kfree(stack);
+out_put_upper:
+	dput(upperdentry);
+out:
+	revert_creds(old_cred);
+	return ERR_PTR(err);
+}
+
+bool ovl_lower_positive(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+	const struct qstr *name = &dentry->d_name;
+	unsigned int i;
+	bool positive = false;
+	bool done = false;
+
+	/*
+	 * If dentry is negative, then lower is positive iff this is a
+	 * whiteout.
+	 */
+	if (!dentry->d_inode)
+		return oe->opaque;
+
+	/* Negative upper -> positive lower */
+	if (!oe->__upperdentry)
+		return true;
+
+	/* Positive upper -> have to look up lower to see whether it exists */
+	for (i = 0; !done && !positive && i < poe->numlower; i++) {
+		struct dentry *this;
+		struct dentry *lowerdir = poe->lowerstack[i].dentry;
+
+		this = lookup_one_len_unlocked(name->name, lowerdir,
+					       name->len);
+		if (IS_ERR(this)) {
+			switch (PTR_ERR(this)) {
+			case -ENOENT:
+			case -ENAMETOOLONG:
+				break;
+
+			default:
+				/*
+				 * Assume something is there, we just couldn't
+				 * access it.
+				 */
+				positive = true;
+				break;
+			}
+		} else {
+			if (this->d_inode) {
+				positive = !ovl_is_whiteout(this);
+				done = true;
+			}
+			dput(this);
+		}
+	}
+
+	return positive;
+}
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index db28512165c5..f6e4d3539a25 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -9,8 +9,6 @@
 
 #include <linux/kernel.h>
 
-struct ovl_entry;
-
 enum ovl_path_type {
 	__OVL_PATH_UPPER	= (1 << 0),
 	__OVL_PATH_MERGE	= (1 << 1),
@@ -138,37 +136,39 @@ static inline struct inode *ovl_inode_real(struct inode *inode, bool *is_upper)
 	return (struct inode *) (x & ~OVL_ISUPPER_MASK);
 }
 
+/* util.c */
+int ovl_want_write(struct dentry *dentry);
+void ovl_drop_write(struct dentry *dentry);
+struct dentry *ovl_workdir(struct dentry *dentry);
+const struct cred *ovl_override_creds(struct super_block *sb);
+struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
+bool ovl_dentry_remote(struct dentry *dentry);
+bool ovl_dentry_weird(struct dentry *dentry);
 enum ovl_path_type ovl_path_type(struct dentry *dentry);
-u64 ovl_dentry_version_get(struct dentry *dentry);
-void ovl_dentry_version_inc(struct dentry *dentry);
 void ovl_path_upper(struct dentry *dentry, struct path *path);
 void ovl_path_lower(struct dentry *dentry, struct path *path);
 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
-int ovl_path_next(int idx, struct dentry *dentry, struct path *path);
 struct dentry *ovl_dentry_upper(struct dentry *dentry);
 struct dentry *ovl_dentry_lower(struct dentry *dentry);
 struct dentry *ovl_dentry_real(struct dentry *dentry);
-struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
-				    bool is_upper);
 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry);
 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache);
-struct dentry *ovl_workdir(struct dentry *dentry);
-int ovl_want_write(struct dentry *dentry);
-void ovl_drop_write(struct dentry *dentry);
 bool ovl_dentry_is_opaque(struct dentry *dentry);
-bool ovl_lower_positive(struct dentry *dentry);
 bool ovl_dentry_is_whiteout(struct dentry *dentry);
 void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
-bool ovl_is_whiteout(struct dentry *dentry);
-const struct cred *ovl_override_creds(struct super_block *sb);
 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
+void ovl_inode_init(struct inode *inode, struct inode *realinode,
+		    bool is_upper);
 void ovl_inode_update(struct inode *inode, struct inode *upperinode);
-struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
-			  unsigned int flags);
+void ovl_dentry_version_inc(struct dentry *dentry);
+u64 ovl_dentry_version_get(struct dentry *dentry);
+bool ovl_is_whiteout(struct dentry *dentry);
 struct file *ovl_path_open(struct path *path, int flags);
 
-struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
-				struct kstat *stat, const char *link);
+/* namei.c */
+int ovl_path_next(int idx, struct dentry *dentry, struct path *path);
+struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags);
+bool ovl_lower_positive(struct dentry *dentry);
 
 /* readdir.c */
 extern const struct file_operations ovl_dir_operations;
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
new file mode 100644
index 000000000000..3b7ba59ad27e
--- /dev/null
+++ b/fs/overlayfs/ovl_entry.h
@@ -0,0 +1,51 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+struct ovl_config {
+	char *lowerdir;
+	char *upperdir;
+	char *workdir;
+	bool default_permissions;
+};
+
+/* private information held for overlayfs's superblock */
+struct ovl_fs {
+	struct vfsmount *upper_mnt;
+	unsigned numlower;
+	struct vfsmount **lower_mnt;
+	struct dentry *workdir;
+	long lower_namelen;
+	/* pathnames of lower and upper dirs, for show_options */
+	struct ovl_config config;
+	/* creds of process who forced instantiation of super block */
+	const struct cred *creator_cred;
+};
+
+/* private information held for every overlayfs dentry */
+struct ovl_entry {
+	struct dentry *__upperdentry;
+	struct ovl_dir_cache *cache;
+	union {
+		struct {
+			u64 version;
+			bool opaque;
+		};
+		struct rcu_head rcu;
+	};
+	unsigned numlower;
+	struct path lowerstack[];
+};
+
+struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
+
+static inline struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
+{
+	return lockless_dereference(oe->__upperdentry);
+}
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 212e746320b3..011482e74096 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -9,283 +9,25 @@
 
 #include <linux/fs.h>
 #include <linux/namei.h>
-#include <linux/pagemap.h>
 #include <linux/xattr.h>
-#include <linux/security.h>
 #include <linux/mount.h>
-#include <linux/slab.h>
 #include <linux/parser.h>
 #include <linux/module.h>
-#include <linux/sched.h>
 #include <linux/statfs.h>
 #include <linux/seq_file.h>
 #include <linux/posix_acl_xattr.h>
 #include "overlayfs.h"
+#include "ovl_entry.h"
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
 MODULE_DESCRIPTION("Overlay filesystem");
 MODULE_LICENSE("GPL");
 
-struct ovl_config {
-	char *lowerdir;
-	char *upperdir;
-	char *workdir;
-	bool default_permissions;
-};
-
-/* private information held for overlayfs's superblock */
-struct ovl_fs {
-	struct vfsmount *upper_mnt;
-	unsigned numlower;
-	struct vfsmount **lower_mnt;
-	struct dentry *workdir;
-	long lower_namelen;
-	/* pathnames of lower and upper dirs, for show_options */
-	struct ovl_config config;
-	/* creds of process who forced instantiation of super block */
-	const struct cred *creator_cred;
-};
 
 struct ovl_dir_cache;
 
-/* private information held for every overlayfs dentry */
-struct ovl_entry {
-	struct dentry *__upperdentry;
-	struct ovl_dir_cache *cache;
-	union {
-		struct {
-			u64 version;
-			bool opaque;
-		};
-		struct rcu_head rcu;
-	};
-	unsigned numlower;
-	struct path lowerstack[];
-};
-
 #define OVL_MAX_STACK 500
 
-static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
-{
-	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
-}
-
-enum ovl_path_type ovl_path_type(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-	enum ovl_path_type type = 0;
-
-	if (oe->__upperdentry) {
-		type = __OVL_PATH_UPPER;
-
-		/*
-		 * Non-dir dentry can hold lower dentry from previous
-		 * location.
-		 */
-		if (oe->numlower && d_is_dir(dentry))
-			type |= __OVL_PATH_MERGE;
-	} else {
-		if (oe->numlower > 1)
-			type |= __OVL_PATH_MERGE;
-	}
-	return type;
-}
-
-static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
-{
-	return lockless_dereference(oe->__upperdentry);
-}
-
-void ovl_path_upper(struct dentry *dentry, struct path *path)
-{
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	path->mnt = ofs->upper_mnt;
-	path->dentry = ovl_upperdentry_dereference(oe);
-}
-
-enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
-{
-	enum ovl_path_type type = ovl_path_type(dentry);
-
-	if (!OVL_TYPE_UPPER(type))
-		ovl_path_lower(dentry, path);
-	else
-		ovl_path_upper(dentry, path);
-
-	return type;
-}
-
-struct dentry *ovl_dentry_upper(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	return ovl_upperdentry_dereference(oe);
-}
-
-struct dentry *ovl_dentry_lower(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	return __ovl_dentry_lower(oe);
-}
-
-struct dentry *ovl_dentry_real(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-	struct dentry *realdentry;
-
-	realdentry = ovl_upperdentry_dereference(oe);
-	if (!realdentry)
-		realdentry = __ovl_dentry_lower(oe);
-
-	return realdentry;
-}
-
-static void ovl_inode_init(struct inode *inode, struct inode *realinode,
-			   bool is_upper)
-{
-	WRITE_ONCE(inode->i_private, (unsigned long) realinode |
-		   (is_upper ? OVL_ISUPPER_MASK : 0));
-}
-
-struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
-				    bool is_upper)
-{
-	if (is_upper) {
-		struct ovl_fs *ofs = inode->i_sb->s_fs_info;
-
-		return ofs->upper_mnt;
-	} else {
-		return oe->numlower ? oe->lowerstack[0].mnt : NULL;
-	}
-}
-
-struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	return oe->cache;
-}
-
-void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	oe->cache = cache;
-}
-
-void ovl_path_lower(struct dentry *dentry, struct path *path)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	*path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
-}
-
-int ovl_want_write(struct dentry *dentry)
-{
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	return mnt_want_write(ofs->upper_mnt);
-}
-
-void ovl_drop_write(struct dentry *dentry)
-{
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	mnt_drop_write(ofs->upper_mnt);
-}
-
-struct dentry *ovl_workdir(struct dentry *dentry)
-{
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	return ofs->workdir;
-}
-
-bool ovl_dentry_is_opaque(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-	return oe->opaque;
-}
-
-bool ovl_dentry_is_whiteout(struct dentry *dentry)
-{
-	return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
-}
-
-void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-	oe->opaque = opaque;
-}
-
-void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
-	WARN_ON(oe->__upperdentry);
-	/*
-	 * Make sure upperdentry is consistent before making it visible to
-	 * ovl_upperdentry_dereference().
-	 */
-	smp_wmb();
-	oe->__upperdentry = upperdentry;
-}
-
-void ovl_inode_update(struct inode *inode, struct inode *upperinode)
-{
-	WARN_ON(!upperinode);
-	WARN_ON(!inode_unhashed(inode));
-	WRITE_ONCE(inode->i_private,
-		   (unsigned long) upperinode | OVL_ISUPPER_MASK);
-	if (!S_ISDIR(upperinode->i_mode))
-		__insert_inode_hash(inode, (unsigned long) upperinode);
-}
-
-void ovl_dentry_version_inc(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	WARN_ON(!inode_is_locked(dentry->d_inode));
-	oe->version++;
-}
-
-u64 ovl_dentry_version_get(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	WARN_ON(!inode_is_locked(dentry->d_inode));
-	return oe->version;
-}
-
-bool ovl_is_whiteout(struct dentry *dentry)
-{
-	struct inode *inode = dentry->d_inode;
-
-	return inode && IS_WHITEOUT(inode);
-}
-
-const struct cred *ovl_override_creds(struct super_block *sb)
-{
-	struct ovl_fs *ofs = sb->s_fs_info;
-
-	return override_creds(ofs->creator_cred);
-}
-
-static bool ovl_is_opaquedir(struct dentry *dentry)
-{
-	int res;
-	char val;
-
-	if (!d_is_dir(dentry))
-		return false;
-
-	res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
-	if (res == 1 && val == 'y')
-		return true;
-
-	return false;
-}
 
 static void ovl_dentry_release(struct dentry *dentry)
 {
@@ -395,275 +137,6 @@ static const struct dentry_operations ovl_reval_dentry_operations = {
 	.d_weak_revalidate = ovl_dentry_weak_revalidate,
 };
 
-static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
-{
-	size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
-	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
-
-	if (oe)
-		oe->numlower = numlower;
-
-	return oe;
-}
-
-static bool ovl_dentry_remote(struct dentry *dentry)
-{
-	return dentry->d_flags &
-		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
-		 DCACHE_OP_REAL);
-}
-
-static bool ovl_dentry_weird(struct dentry *dentry)
-{
-	return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
-				  DCACHE_MANAGE_TRANSIT |
-				  DCACHE_OP_HASH |
-				  DCACHE_OP_COMPARE);
-}
-
-static inline struct dentry *ovl_lookup_real(struct dentry *dir,
-					     const struct qstr *name)
-{
-	struct dentry *dentry;
-
-	dentry = lookup_one_len_unlocked(name->name, dir, name->len);
-	if (IS_ERR(dentry)) {
-		if (PTR_ERR(dentry) == -ENOENT)
-			dentry = NULL;
-	} else if (!dentry->d_inode) {
-		dput(dentry);
-		dentry = NULL;
-	} else if (ovl_dentry_weird(dentry)) {
-		dput(dentry);
-		/* Don't support traversing automounts and other weirdness */
-		dentry = ERR_PTR(-EREMOTE);
-	}
-	return dentry;
-}
-
-/*
- * Returns next layer in stack starting from top.
- * Returns -1 if this is the last layer.
- */
-int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	BUG_ON(idx < 0);
-	if (idx == 0) {
-		ovl_path_upper(dentry, path);
-		if (path->dentry)
-			return oe->numlower ? 1 : -1;
-		idx++;
-	}
-	BUG_ON(idx > oe->numlower);
-	*path = oe->lowerstack[idx - 1];
-
-	return (idx < oe->numlower) ? idx + 1 : -1;
-}
-
-struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
-			  unsigned int flags)
-{
-	struct ovl_entry *oe;
-	const struct cred *old_cred;
-	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
-	struct path *stack = NULL;
-	struct dentry *upperdir, *upperdentry = NULL;
-	unsigned int ctr = 0;
-	struct inode *inode = NULL;
-	bool upperopaque = false;
-	bool stop = false;
-	bool isdir = false;
-	struct dentry *this;
-	unsigned int i;
-	int err;
-
-	old_cred = ovl_override_creds(dentry->d_sb);
-	upperdir = ovl_upperdentry_dereference(poe);
-	if (upperdir) {
-		this = ovl_lookup_real(upperdir, &dentry->d_name);
-		err = PTR_ERR(this);
-		if (IS_ERR(this))
-			goto out;
-
-		if (this) {
-			if (unlikely(ovl_dentry_remote(this))) {
-				dput(this);
-				err = -EREMOTE;
-				goto out;
-			}
-			if (ovl_is_whiteout(this)) {
-				dput(this);
-				this = NULL;
-				stop = upperopaque = true;
-			} else if (!d_is_dir(this)) {
-				stop = true;
-			} else {
-				isdir = true;
-				if (poe->numlower && ovl_is_opaquedir(this))
-					stop = upperopaque = true;
-			}
-		}
-		upperdentry = this;
-	}
-
-	if (!stop && poe->numlower) {
-		err = -ENOMEM;
-		stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
-		if (!stack)
-			goto out_put_upper;
-	}
-
-	for (i = 0; !stop && i < poe->numlower; i++) {
-		struct path lowerpath = poe->lowerstack[i];
-
-		this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
-		err = PTR_ERR(this);
-		if (IS_ERR(this)) {
-			/*
-			 * If it's positive, then treat ENAMETOOLONG as ENOENT.
-			 */
-			if (err == -ENAMETOOLONG && (upperdentry || ctr))
-				continue;
-			goto out_put;
-		}
-		if (!this)
-			continue;
-		if (ovl_is_whiteout(this)) {
-			dput(this);
-			break;
-		}
-		/*
-		 * If this is a non-directory then stop here.
-		 */
-		if (!d_is_dir(this)) {
-			if (isdir) {
-				dput(this);
-				break;
-			}
-			stop = true;
-		} else {
-			/*
-			 * Only makes sense to check opaque dir if this is not
-			 * the lowermost layer.
-			 */
-			if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
-				stop = true;
-		}
-
-		stack[ctr].dentry = this;
-		stack[ctr].mnt = lowerpath.mnt;
-		ctr++;
-	}
-
-	oe = ovl_alloc_entry(ctr);
-	err = -ENOMEM;
-	if (!oe)
-		goto out_put;
-
-	if (upperdentry || ctr) {
-		struct dentry *realdentry;
-		struct inode *realinode;
-
-		realdentry = upperdentry ? upperdentry : stack[0].dentry;
-		realinode = d_inode(realdentry);
-
-		err = -ENOMEM;
-		if (upperdentry && !d_is_dir(upperdentry)) {
-			inode = ovl_get_inode(dentry->d_sb, realinode);
-		} else {
-			inode = ovl_new_inode(dentry->d_sb, realinode->i_mode,
-					      realinode->i_rdev);
-			if (inode)
-				ovl_inode_init(inode, realinode, !!upperdentry);
-		}
-		if (!inode)
-			goto out_free_oe;
-		ovl_copyattr(realdentry->d_inode, inode);
-	}
-
-	revert_creds(old_cred);
-	oe->opaque = upperopaque;
-	oe->__upperdentry = upperdentry;
-	memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
-	kfree(stack);
-	dentry->d_fsdata = oe;
-	d_add(dentry, inode);
-
-	return NULL;
-
-out_free_oe:
-	kfree(oe);
-out_put:
-	for (i = 0; i < ctr; i++)
-		dput(stack[i].dentry);
-	kfree(stack);
-out_put_upper:
-	dput(upperdentry);
-out:
-	revert_creds(old_cred);
-	return ERR_PTR(err);
-}
-
-bool ovl_lower_positive(struct dentry *dentry)
-{
-	struct ovl_entry *oe = dentry->d_fsdata;
-	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
-	const struct qstr *name = &dentry->d_name;
-	unsigned int i;
-	bool positive = false;
-	bool done = false;
-
-	/*
-	 * If dentry is negative, then lower is positive iff this is a
-	 * whiteout.
-	 */
-	if (!dentry->d_inode)
-		return oe->opaque;
-
-	/* Negative upper -> positive lower */
-	if (!oe->__upperdentry)
-		return true;
-
-	/* Positive upper -> have to look up lower to see whether it exists */
-	for (i = 0; !done && !positive && i < poe->numlower; i++) {
-		struct dentry *this;
-		struct dentry *lowerdir = poe->lowerstack[i].dentry;
-
-		this = lookup_one_len_unlocked(name->name, lowerdir,
-					       name->len);
-		if (IS_ERR(this)) {
-			switch (PTR_ERR(this)) {
-			case -ENOENT:
-			case -ENAMETOOLONG:
-				break;
-
-			default:
-				/*
-				 * Assume something is there, we just couldn't
-				 * access it.
-				 */
-				positive = true;
-				break;
-			}
-		} else {
-			if (this->d_inode) {
-				positive = !ovl_is_whiteout(this);
-				done = true;
-			}
-			dput(this);
-		}
-	}
-
-	return positive;
-}
-
-struct file *ovl_path_open(struct path *path, int flags)
-{
-	return dentry_open(path, flags | O_NOATIME, current_cred());
-}
-
 static void ovl_put_super(struct super_block *sb)
 {
 	struct ovl_fs *ufs = sb->s_fs_info;
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
new file mode 100644
index 000000000000..0d45a84468d2
--- /dev/null
+++ b/fs/overlayfs/util.c
@@ -0,0 +1,235 @@
+/*
+ * Copyright (C) 2011 Novell Inc.
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/slab.h>
+#include <linux/xattr.h>
+#include "overlayfs.h"
+#include "ovl_entry.h"
+
+int ovl_want_write(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	return mnt_want_write(ofs->upper_mnt);
+}
+
+void ovl_drop_write(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	mnt_drop_write(ofs->upper_mnt);
+}
+
+struct dentry *ovl_workdir(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	return ofs->workdir;
+}
+
+const struct cred *ovl_override_creds(struct super_block *sb)
+{
+	struct ovl_fs *ofs = sb->s_fs_info;
+
+	return override_creds(ofs->creator_cred);
+}
+
+struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
+{
+	size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
+	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
+
+	if (oe)
+		oe->numlower = numlower;
+
+	return oe;
+}
+
+bool ovl_dentry_remote(struct dentry *dentry)
+{
+	return dentry->d_flags &
+		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
+		 DCACHE_OP_REAL);
+}
+
+bool ovl_dentry_weird(struct dentry *dentry)
+{
+	return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
+				  DCACHE_MANAGE_TRANSIT |
+				  DCACHE_OP_HASH |
+				  DCACHE_OP_COMPARE);
+}
+
+enum ovl_path_type ovl_path_type(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	enum ovl_path_type type = 0;
+
+	if (oe->__upperdentry) {
+		type = __OVL_PATH_UPPER;
+
+		/*
+		 * Non-dir dentry can hold lower dentry from previous
+		 * location.
+		 */
+		if (oe->numlower && d_is_dir(dentry))
+			type |= __OVL_PATH_MERGE;
+	} else {
+		if (oe->numlower > 1)
+			type |= __OVL_PATH_MERGE;
+	}
+	return type;
+}
+
+void ovl_path_upper(struct dentry *dentry, struct path *path)
+{
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	path->mnt = ofs->upper_mnt;
+	path->dentry = ovl_upperdentry_dereference(oe);
+}
+
+void ovl_path_lower(struct dentry *dentry, struct path *path)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	*path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
+}
+
+enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
+{
+	enum ovl_path_type type = ovl_path_type(dentry);
+
+	if (!OVL_TYPE_UPPER(type))
+		ovl_path_lower(dentry, path);
+	else
+		ovl_path_upper(dentry, path);
+
+	return type;
+}
+
+struct dentry *ovl_dentry_upper(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	return ovl_upperdentry_dereference(oe);
+}
+
+static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
+{
+	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
+}
+
+struct dentry *ovl_dentry_lower(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	return __ovl_dentry_lower(oe);
+}
+
+struct dentry *ovl_dentry_real(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	struct dentry *realdentry;
+
+	realdentry = ovl_upperdentry_dereference(oe);
+	if (!realdentry)
+		realdentry = __ovl_dentry_lower(oe);
+
+	return realdentry;
+}
+
+struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	return oe->cache;
+}
+
+void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	oe->cache = cache;
+}
+
+bool ovl_dentry_is_opaque(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	return oe->opaque;
+}
+
+bool ovl_dentry_is_whiteout(struct dentry *dentry)
+{
+	return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
+}
+
+void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	oe->opaque = opaque;
+}
+
+void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
+	WARN_ON(oe->__upperdentry);
+	/*
+	 * Make sure upperdentry is consistent before making it visible to
+	 * ovl_upperdentry_dereference().
+	 */
+	smp_wmb();
+	oe->__upperdentry = upperdentry;
+}
+
+void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
+{
+	WRITE_ONCE(inode->i_private, (unsigned long) realinode |
+		   (is_upper ? OVL_ISUPPER_MASK : 0));
+}
+
+void ovl_inode_update(struct inode *inode, struct inode *upperinode)
+{
+	WARN_ON(!upperinode);
+	WARN_ON(!inode_unhashed(inode));
+	WRITE_ONCE(inode->i_private,
+		   (unsigned long) upperinode | OVL_ISUPPER_MASK);
+	if (!S_ISDIR(upperinode->i_mode))
+		__insert_inode_hash(inode, (unsigned long) upperinode);
+}
+
+void ovl_dentry_version_inc(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	WARN_ON(!inode_is_locked(dentry->d_inode));
+	oe->version++;
+}
+
+u64 ovl_dentry_version_get(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	WARN_ON(!inode_is_locked(dentry->d_inode));
+	return oe->version;
+}
+
+bool ovl_is_whiteout(struct dentry *dentry)
+{
+	struct inode *inode = dentry->d_inode;
+
+	return inode && IS_WHITEOUT(inode);
+}
+
+struct file *ovl_path_open(struct path *path, int flags)
+{
+	return dentry_open(path, flags | O_NOATIME, current_cred());
+}